Weak Laser Signal Spectrum Detection Method Using The Double-wedge Interferometer

The use of interferometer to detect and analyze laser radiation is well known,but when the intense ratio of the laser radiation to the background natural light radiation is too small, the laser radiation cannot be detected.A novel more sensitive method for detect of wideband weak incident laser in strong background noise is introduced in this paper.The optical unit uses two wedge interferometers and two line array detectors.The incoming light radiation is divided into two beams and through the interferometers. Two wedge interferometers are designed that the thickness of one is higher than the other.So when the incident coherent light through the interferometers can acquire two fringe patterns which having space shift,but the incident incoherent light only result in consistent intensity signal.Through a differentiating amplifier,two signals subtract which can eliminate noise of background and result in higher contrast ratio fringe signals.This method largely improves the system and the ability of detection.The spacing of line fringes is a function of incident laser wavelength,by analyzing, we can extract the wavelength of incident laser.The optical unit analyzing and results also simulated with matlab.